30 CFR § 57.22230
Weekly testing (II-A mines).
(a) The mine atmosphere shall be tested for methane at least once
every seven days by a competent person or an atmospheric monitoring system,
or a combination of the two. Such testing shall be done at the following
locations:
(1) Active mining faces and benches;
(2) Main returns;
(3) Returns from idle workings;
(4) Returns from abandoned workings; and
(5) Seals.
(b) Where such examinations disclose hazardous conditions, affected
persons shall be informed and corrective action shall be taken.
(c) Certification of examinations shall be made by signature and
date. Certifications shall be kept for at least one year and made available
to authorized representatives of the Secretary.
[52 FR, 24941, July 1, 1987, as amended at 52 FR 41397, Oct. 27, 1987; 60 FR
33719, June 29, 1995]